net: Add ESP offload features

This patch adds netdev features to configure IPsec offloads.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 741d75c..81ef53f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -492,6 +492,8 @@ enum {
 	SKB_GSO_TUNNEL_REMCSUM = 1 << 14,
 
 	SKB_GSO_SCTP = 1 << 15,
+
+	SKB_GSO_ESP = 1 << 16,
 };
 
 #if BITS_PER_LONG > 32